billionaire warren buffett chimes in that tax hikes won't stop the wealthy from investing. in our cover story, the woman who led the securities and exchange commission after the 2008 financial crisis is stepping down. mary schapiro took over an agency under fire for ignoring repeated warnings about the bernie madoff ponzi scheme. in 2008, the regulatory sec was itself under scrutiny, critized for failing to anticipate the lehman brothers bankruptcy, which sent financial markets reeling, and also missing the warning signs of bernie madoff's multi-billion dollar ponzi scheme. "before she got there, they almost needed someone to come in and confess." mary schapiro, who president obama said will be replaced by commissioner elisse walter, overhauled sec enforcement and made it more proactive. "to get out there and defend investors, as opposed to trying to figure out what happened after." but critics say for the dozens of insider trading investigations, the sec under schapiro did not crack down on top executives during the financial crisis or since. "the mf global mess - is anyon